It is known from Rice U.S. Pat. No. 2,550,498 that vapors of various halogen compounds are readily detected in minute quantities in the atmosphere. Sensitivities of one part vapor to a million parts of air (volume basis) are readily achieved. It would be useful to have a detector of similar or even greater sensitivity for the detection of low molecular weight hydrocarbons, ketones and alcohols, such as, for example, methane, ethane, acetone, ethanol and others. Other known vapor or chemical detection methods or systems are found in the following U.S. Pat. Nos.:
3,410,663 to Reilly et al. on Nov. 12, 1968;
3,039,053 to Jacobson on Apr. 10, 1959;
2,550,498 to Rice on Apr. 24, 1951;
3,842,345 to Padgitt et al on Oct. 15, 1974;
3,903,726 to Hirosawa et al on Sept. 9, 1975;
3,725,895 to Haynes on Apr. 3, 1973;
2,283,262 to Kamlet on May 19, 1942;
3,498,309 to Vonderschmitt et al on May 1, 1967;
3,824,079 to Veneme on July 16, 1974;
3,536,088 to Moyat on Oct. 27, 1970;
3,065,411 to Roberts on Nov. 20, 1962;
3,711,251 to Goodson on Jan. 10, 1973.
In the Goodson patent, air containing organic vapor is introduced into a "converter" in which organic vapor, such as organic alcohol, is caused to react with a solid or liquid reactive halogen compound, such as phosphorous pentachloride, contained in the converter. The halogenation reaction produces a halogenated organic compound which is subsequently sensed to detect the presence of organic vapor in the sample undergoing test. It is stated in the Goodson patent that an ethyl alcohol vapor content on the order of 20 gammas per liter of air may be detected. This corresponds to a sensitivity, on a volume basis, of about 9700 parts per billion. Assuming that the same sensitivity of 20 gammas can be achieved with acetone, this corresponds to a sensitivity, on a volume basis, of about 7700 parts per billion. While this sensitivity is good, even greater sensitivity is highly desirable.